For decades, virtually all urban growth in the high-income world has been in the suburbs, outside the
historical core cities Nearly 96 percent of urban growth has been in the suburbs..
But even growth within the core cities can be suburban or non-densifying, if there is substantial undeveloped land within the city's boundaries or if there
are annexations or municipal amalgamations. For example, much of the population growth in Rome, New York, Los Angeles and Nagoya can be attributed to
development of open land within the city. Examples of cities growing due to amalgamation or annexation include Antwerp, Kitakyushu, Auckland, Portland
and Milwaukee. For example, since 1950 Portland has annexed 110 percent more land than it occupied in 1950, yet has less than 50 percent more people.
This analysis classifies the core cities that have achieved (at some point) 400,000 residents as follows:

1. Fully Developed: Densifying
Core cities that have substantially retained their 1950 boundaries, inside of which there has been little undeveloped land, and which are at their peak population. There is a single example, Vancouver, Canada.

2. Fully Developed: Not DensifyingCore cities that have substantially retained their 1950 boundaries, inside of which there has been little undeveloped land, and have lost population. There are
73 examples. (Some core cities are now growing again, but generally remain far below their peak populations). Overall, these cities have lost nearly
20 percent of their population, dropping from 88.0 million to 70.7 million.

3. Not Fully Developed: Population at PeakCore cities that have expanded their boundaries since 1950 or have had substantial tracts of undeveloped land. For example, while New York is at its population peak, much of
two boroughs (Queens and Richmond) had substantial amounts of undeveloped land in 1950. The three remaining boroughs, all of which were fully developed in 1950
remain below their population peaks.

4. Not Fully Developed: Population FallingCore cities that have expanded their boundaries since 1950 or have had substantial tracts of undeveloped land and have lost population. For example, the
US city of Milwaukee nearly doubled its area by annexation during the 1950s. Yet the latest estimates show its population to be below the pre-annexation
1950 figure.